Sui (スイ) is a member of Sunset Ravens. In addition to herself, there is the soul of her deceased brother Souta (ソータ) inside of her, and they are able to swap if needed.
Sui has long pale blue hair and eyes of the same color. She usually wears a white hooded coat with cat ears and black tights.
After the 5 year timeskip, Sui now has longer hair which extends down to her stomach. She wears a dark top, an open coat similar to the hooded one she wore before, and long dark tights.
Sui is a shy girl and dislikes killing others to survive. Before going to the Out of Range Village, she was timid and passive, sticking to support roles like Kashiwagi Rein. During the battle against Eighth, she threw up upon seeing the aftermath of Kaname and Ryuuji's massacre of Eighth members. However, during their stay at the village, she began to get involved and helped everyone find the culprit, in addition to neutralizing the threat herself. Despite normally being passive, she is dependable when it comes down to it, such as confronting who she thought was the culprit and capturing Oboro before he could escape. She also cares about her fellow clan members, as she felt guilty of not being able to prevent Ryuuji from being attacked while they were in the village.
After the timeskip, Sui is shown to be much more ruthless, asking Kaname if he wanted her to suffocate Oboro upon capturing him, and later asked Kaname if he wanted to make Oboro feel like he was drowning.
Unlike Sui, Souta is much more bold and outspoken, and is not averse to killing others. He is shown to not think things through, telling those present that they should kill the enemy rather than think too hard about it, causing Rein to explain why it wasn't so easy, and when he panicked when the fake Kazuya died, stating that he didn't freeze him that deep. People don't believe he actually exists and think that he is an alter ego of Sui.
Pollux Light (
After the timeskip, Sui is shown to have greater control over her sigil, being able to use it unconsciously while thinking about other things. She has improved the speed at which she can control water, as she was able to stop Oboro from flying away and quickly trap him inside water.
Castor Light (
- Despite being cowardly, Sui is mentioned to be skilled at playing violent video games.
- Sui and Souta's sigils are a reference to Castor and Pollux.